The co-ordination of insect movements. III. Swimming in Dytiscus kydrophilw and a dragonfly nymph

Although many of the structural adaptations associated with the locomotion of aquatic insects are well known, there are few observations on the details of their propulsive mechanisms. In general, these may be subdivided into those which effect swimming by undulatory movements of the body (Kalmus, 1936; Gray, 1953), by oar-like movements of the legs or wings (e.g. Polynema, Hymenoptera), or by jet propulsion methods involving either the use of a surface active secretion (Stenus, Staphylinidae) or the active expulsion of water from the insect. Of these the use of legs as oars is the most common among adults. In this paper cinemato-graphic analyses are given of two beetles which use this method and of the abdominal and leg movements involved in the jet propulsion of a dragonfly nymph. In addi-tion, some observations are described on the effect of amputating legs on the swimming of Dytiscus. These differ significantly from the observations of Bethe & Woitas (1930) and support conclusions based on a study of cockroach movements (Hughes, 1957). MATERIALS AND METHOD